Highly polymorphic Alu loci will be used as genetic markers to refine the human genetic linkage map. A refined genetic map is important for mapping inherited disease genes, for studying loss of heterozygosity, and for constructing a physical map of the human genome. Regions flanking Alu elements from various loci will be sequenced and PCR primers will be developed to amplify the Alu elements. PCR products from unrelated individuals will be screened for their ability to reveal polymorphisms by PAGE, DGGE (denaturing gradient gel electrophoresis), and SSCP (single-stranded conformation polymorphism) techniques. The polymorphic loci will then be mapped genetically. Such a PCR based genotyping method will be a significant improvement over currently used genomic Southern hybridization methods. The oligonucleotides developed in this research will be an important research product for human genome research. In some cases they can also be used for the diagnosis of genetic diseases and tumors, and for identity testing.